The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
Organosilicon dendritic and hyperbranched polymers are well known. The dendrirner core is usually prepared from tetraallyl- or -vinylsilane, which is then derivatized by hydrosilylation reaction (1, 2). On the other hand, hyperbranched polycarbosilanes are commonly prepared from vinyltris(dimethylsiloxy)silane via hydrosilylation reactions. Typically, 8-10 mol-% starting material cyclizes in a side reaction (3). See Scheme 1.
There are few examples of hyperbranched or dendritic polysiloxanes, eg. polymers, whose backbone consist only of --SiRR'--O-- linkages. Probably the most significant paper is by Uchicda et al. (4) which describes a multistep pathway for highly regular third generation dendritic polysiloxanes with molecular weight of about 15,000 g/mol. See Scheme 2.
Rebrov (5) used a different approach. He let MeSiCl.sub.3 react with three equivalents of NaOSiMe(OEt).sub.2. Ethoxy groups were then converted quantitatively into chlorines by reaction with thionyl chloride. Treatment of the resulting product again with NaOSiMe(OEt).sub.2, followed by conversion of the Si--OEt into Si--Cl groups repeatedly gave a fourth generation polymer in &gt;75% yield. See Scheme 3.
Morikowa (6) utilized easily cleavageable Si--Ph bond in his synthesis. The core was prepared from a compound having three Si-phenyl groups which were converted into Si--Br by treatmnent of Br.sub.2. Reaction with HNMe.sub.2 gave Si--N functionalities, which in turn could be reacted with silanols bearing Si-phenyl groups. This cycle was repeated two times to give a 3.sup.rd generation dendrimer in 32% yield, with a molecular weight of about 4,800 g/mol. See Scheme 4. ##STR1## ##STR2## ##STR3## ##STR4##